166721947 has 4 divisors (see below), whose sum is σ = 190539376. Its totient is φ = 142904520.

The previous prime is 166721939. The next prime is 166721953. The reversal of 166721947 is 749127661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 166721947 - 2³ = 166721939 is a prime.

It is a super-2 number, since 2×166721947² = 55592415222941618, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166721977) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11908704 + ... + 11908717.

It is an arithmetic number, because the mean of its divisors is an integer number (47634844).

Almost surely, 2^166721947 is an apocalyptic number.

166721947 is a deficient number, since it is larger than the sum of its proper divisors (23817429).

166721947 is an equidigital number, since it uses as much as digits as its factorization.

166721947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23817428.

The product of its digits is 127008, while the sum is 43.

The square root of 166721947 is about 12912.0853079586. The cubic root of 166721947 is about 550.3820453031.

The spelling of 166721947 in words is "one hundred sixty-six million, seven hundred twenty-one thousand, nine hundred forty-seven".